Process of treating coils.



UNITED STATES PATENT curios.

JOSEPH I. MITCHELL, 0F PITTSFIELD, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

PROCESS OF TREATING COILS.

No Drawing.

To all whom it may concern:

Be it-known that I, JosEPn I. MITCHELL, a citizen of the United States, residing at- Pittsfield, county "of Berkshire, State of Massachusetts, have invented certain new and useful Improvements in Processes of Treating Coils, of which the following is a specification.

This invention relates to the treatment of coils for electrical purposes and has for its object the provision of means whereby a coil may be produced which will have certain desirable properties, adapting it for particular uses in the electrical art. l

My invention relates more particularly to the production of coils for use in transformers and the.like where the coils are cooled in oil and it is necessary that a film be provided which will be proof against the action of the oil.

In the manufacture of transformer coils, it is common 'to wind them into the desired form and then remove the winding forms and impregnate them with certain materials. It is desirable that the material with which 'the' coil is impregnated shall have sufiicient cohesive strength to hold the coils together when the winding forms are removed. The oil-proof films which have been employed do not have sufiicient cohesive strength for this purpose.

One of the objects of my invention is to overcome this ditliculty. I have found that by first impregnating the coil with a material which may be hardened at a relatively low temperature and then impregnating with a second material and hardening at a high temperature, a very satisfactory result may be obtained. /l3y first employing a material which is relatively cohesive but not necessarily oil-proof, I am enabled to use for the second impregnation a material which has less cohesive strength but which has the other desired properties. In carrying out my invention, therefore, I first wind the coils in the desired shape-and impregnate them with a material which, when hardened, will have a relatively high 00- hesive strength. It is also-desirable that this material shall be one which will harden at a relatively low temperature. I have found such a materiaLin 'apan which, when harcle ed, will have an cient' mechanical 'streng hi'to hold the coil in shape. -.I have Specification of Letters Patent. Application filed March 12, 1910, Serial No. 548,955.

Patented Dec-.5, 1911.

also found that this material, when employed in connection with a second material having oil-proof properties, will amalgamate with the second material to produce a vlery elastic and satisfactory film over the CO1 In practice my' invention is carried out in the following manner: The coil, after being wound to the desired shape on the winding form, is treated with japan and hardened preferably by baking. lVhen this japan is hardened it has suificienkcohesiveness to hold the coil to "shape when the winding form is removed. The japan, which commonly consists of asphalt and linseed oil thinned with a solvent such as turpentine or the like, does not however have the C19, sired oil-proof property. A tape, commonly known as stripping tape is now/wound upon the coil to hold it permanently in place and the coil is then impregnated with an oil-proof compound. This compound may be of any suitable composition but preferably one which hardens at a higher temperature than the japan and which will amalgamate with it. I have found that a com? pound composed of copal gum and a small percentage of rosin and castor oil makes a satisfactory oil-proof material and serves my purpose very well. This material, when baked at a higher temperature than that at which the japan is baked, amalgamates with the japan and forms an elastic oil-proof film. Briefly summarized, the advantages of this manner of treatment are that the japan holds the coils after the winding forms have been removed and before the stripping tape is put into place. The oilproof compound when applied alone is more or less brittle and flakes ofi the surface of the coil. It would, therefore, not be suitable for holding the coil in place unless hand-led very carefully. When applied, however, in accordance with my invention, the oil-proof compound amalgamates with the japan to provide the desired properties for the coil such as being tough and oil-proof.

, While I have described my process as employing specific materials operated upon in a definite manner to produce certain specific results, it should be understood that I do.

not limit my invention thereto, since various modifications thereof 'will suggest them selves to those skilled in the art without departing from the spirit of my invention, the scope of which is set'forth in the annexed claims.

What I claim as new and desire to secure by Letters Patent of the United States, is,-

l. The process of treating transformer coils 01" the like which consists in impregnating them with japan and hardening at a relatively low temperature to hold the turns in place, and then impregnating with another material and hardening at a higher temperature.

2. The process of treating transformer coils or the like which consists in impregnating them with japan and hardening at a relatively low temperature to hold theturns in place, and then impregnating with another material which will'amalgamate with the first and hardening at a higher temperature. 4

3. The process of treating transformer coils or the like which consists in impregnating them with a relatively cohesive material to hold the turns in place, and then impregnating with another material which is oil-proof but less cohesive than the first material. 4. The process of treating transformer coils or the like which consists in impregnating them with a material and baking them hard at arelatively low temperature to hold the turns in place, and then impregnating with another material which will amalgamate with the first material and harden at a higher temperature.

5. The process of treating transformer coils or the like which consists in impregnating them with a material and hardening at a relatively low temperature to hold the turns in place,.and then impregnating with another material and hardening at a higher temperature.

6. The process of treating transformer coils or the like which consists in impregnatingthem with a material and hardening at a relatively low temperature to hold the turns in place, and then impregnating with another material whlch will amalgamate with the first material and baking at a higher temperature.

7. The process of-treating transformer coils or the like which consists in impregnating them with japan and hardening at a low temperature to hold the turns in place, and then impregnating with an oil-proof material and hardening at a higher temperature.

8. The process of treating transformer coils or the like which consists in impregnating them with japan and hardening ata relatively low temperature to hold the turns in place, and then impregnating with an oil-proof material which will amalgamate with the first material and hardening at a temperature which will cause the materials to amalgamate.

9. The process of treating transformer coils or the like which consists in impregnating them with a material and hardening at a relatively low temperature to hold the turns in place, and then impregnating with a second material which will, amalgamate with the first material and hardening at a higher temperature.

10. The process of treating transformer 'coils or the like which consists in impregnating them with a non oil-proof relatively cohesive material to hold the turns in place,

hardening said material, and then impregnating with an oil-proof but less cohesive material which will amalgamate with the first material, and heating to a temperature at which the materials will amalgamate.

11. The process of treating transformer coils or the like which consists in impregnating them with a relatively low cohesive material and baking hard to hold the turns inplace, winding the coil with tape, and

then impregnating with an oil proof material.

12. The process of treating transformer;

coils or the like which consists in impregnating them with japan and hardening at a relatively low temperature to hold the turns in place, winding the coil with tape, and impregnating with oil proof material and hardening ata higher temperature.

In witness whereof, I have hereunto set my hand this 9th day of March, 1910.

I JOSEPH I. MITCHELL. \Vitnesses:

CHARLES S. MEIGs, W. W. VAN DEUsEN.

copies of 1:111! patent my be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. 0. i 

